Development and Tests of a Low Cost Passive Millimeter Wave Sensor

摘要

This report describes an effort to develop and test a passive millimeter wave(PMMW) sensor for application as a physical security sensor. It also describes the successful implementation of a total power radiometer at 27.7-GHz center frequency as the sensor. The sensor that was demonstrated was completely fabricated from printed circuit board components. The architecture of the down converter was coplanar waveguide. This means that no via-holes were required for the rf section. All the critical elements of the receiver were demonstrated with low cost components. The thermal resolution of the radiometer was better than 0.1 K. Testing showed that the sensor performed comparably to a passive infrared (PIR) sensor in most interior environments. Tests were conducted with simultaneous measurements by colocated sensors so that direct comparisons could be made between the PIR and the PMMW sensor. The PMMW sensor was less susceptible to evasive efforts, especially simple techniques. The PMMW sensor appeared to perform much better in an exterior environment. Reliable exterior target detections were made at a range of 200 ft with a single sensor. Furthermore, the sensor still detected targets at 200 ft when the ambient temperature was 99 deg F. This has significant application in areas such as desert and coastal environments. Estimates for the probability of detection and probability of false alarm which are based on the measured data are provided for both the PIR sensor and the PMMW sensors. These estimates show that the PMMW sensor can provide good probability of detection with a low probability of false alarm in both the interior and the exterior environment. The PIR sensor, in contrast, can provide good detections only in the interior environment and made no detections in the exterior environment testing performed.